The polymerization of olefins is well known and has been a widely practiced commercial art for many decades. Catalysts for such polymerization are well known to include Ziegler-Natta type catalysts. In the Ziegler-Natta type catalyst field, the catalyst is usually made up of a transition metal compound such as titanium tetrachloride and an alkyl aluminum as a co-catalyst such as trimethyl or triethyl aluminum
However, in order to improve physical properties of polymers of olefins, various researches and developments on catalysts having a high polymerization activity have been carried out. In this regard, metallocene catalysts have been developed, which are superior in polymerization activity and stereoregularity to Ziegler-Natta type catalysts.
U.S. Pat. No. 4,808,561 to Welborn, Jr. discloses an olefin polymerization catalyst comprising the supported reaction product of at least one metallocene of a metal of Group IVb of the Periodic Table and an aluminoxane. The reaction product is formed in the presence of the support which is a porous inorganic metal oxide of Group 2a, 3a, 4a or 4b metal.
U.S. Pat. No. 4,921,825 to Kioka et al. discloses a process for preparing a solid catalyst for olefin polymerization from an aluminoxane, a compound of a transition metal of Group IVb of the Periodic Table and a certain organic or inorganic compound carrier, which comprises contacting a solution of said aluminoxane in a first solvent with a second solvent in which the aluminoxane is insoluble, in the presence of said certain organic or inorganic compound carrier, to deposit said aluminoxane on said certain organic or inorganic compound carrier.
U.S. Pat. No. 5,122,491 discloses a catalyst useful for the polymerization of an olefin prepared from (A) a compound selected from the group consisting of zirconium and hafnium compounds having a ligand including conjugated .pi. electron, (B) an aluminoxane, and (C) an organoaluminum compound.
U.S. Pat. No. 5,362,824 discloses a polymerization catalyst comprising at least one metallocene and at least one aluminoxane dispersed on the surface of a resinous substrate comprising a cross-linked copolymer of about 30% divinyl benzene, about 55% styrene, and about 15% of acetoxy or hydroxy styrene.
Typically, homogeneous metallocene catalysts are capable of producing an olefin polymer having a narrow molecular-weight distribution and a stereoregularity. However, the homogeneous metallocene catalysts are disadvantageous in polymer morphology, shape and size of polymer particle, and bulk density. Accordingly, intensive researches are focused on heterogeneous metallocene catalysts for olefin polymerization. Some heterogeneous metallocene catalysts supported on an inorganic carrier such as SiO.sub.2, Al.sub.2 O.sub.3 or MgCl.sub.2 have already been developed. In particular, the heterogeneous metallocene catalysts can prepare a polypropylene having high stereoregularity.
In order to provide a metallocene catalyst for preparing an olefin polymer having improved properties, the present inventors have developed a new process for preparing an organic carrier supported metailocene catalyst useful for polymerization of olefins.